The present invention relates to a cutting insert primarily for cutting-off operations. However, if so desired, it may also be used for grooving. Suitably, the insert is made of coated or uncoated cemented carbide, but other hard materials may also be used, such as different ceramic materials and so called cermets.
Cutting-off and deep radial and axial grooving are performed with tools which are normally referred to as parting and grooving tools. Characteristic for inserts and tools of this type is their small axial extension. The reason for this is of course that material for making the tools shall not be unnecessarily wasted, and also to make possible the machining of grooves of a smaller width.
A typical insert for cutting-off is disclosed in Pettersson et al. U.S. Pat. No. 4,801,224. However, for some cutting-off operations, also this insert is too wide, because too much material from the workpiece is wasted in the form of chips. The inserts according to this citation are made with a smallest width of 2 mm, since even smaller insert widths are not considered to be safely fastenable to a holder. Moreover, the inserts become too fragile.
Another cutting insert for cutting-off and grooving is disclosed in Schmidt U.S. Pat. No. 5,529,440. This one has a relatively thin, quadrangular basic shape, with a cutting edge provided in each corner. However, the relation between the insert's extension and thickness is too large to make it tenable. Therefore, it is usually made of high speed steel instead of cemented carbide, which of course results in a considerable deterioration in the cutting performance.
Thus, a first object of the present invention is to construct a cutting insert primarily intended for cutting-off, which makes possible very small cutting widths, for instance down to 0.4 mm.
A second object of the present invention is to provide a cutting-off insert that is as thin as possible but also as strong as possible.
Still another object of the present invention is to provide a cutting-off insert that is as thin as possible and does not make necessary any changes of the other equipment, such as for instance the holder blade.